The proposed study would form a continuation of personal work on the organization of sensory pathways, particularly the somesthetic, in the mammalian forebrain. One part, to be carried out with conventional light microscopic (Nauta) techniques, would be an analysis of the cortical projections of the posterior group of thalamic nuclei in the monkey. It is hoped that this would contribute to our understanding of central nervous mechanisms in pain. A second part would be a detailed analysis of the cellular and synaptic organization of the postcentral gyrus of the monkey using a variety of light and electron microscopic techniques. The object would be to provide quantitative as well as qualitative data with particular emphasis on possible morphological correlates of the electrophysiological cell columns.